Method of driving liquid crystal display and liquid crystal display using the driving method

Abstract

In a method of driving an active matrix liquid crystal display according to pulse width modulation driving system using a thin-film transistor for a switching device, the variation of the temperature of a liquid crystal display panel is monitored. Particularly, the panel temperature detecting means of the liquid crystal display panel is provided, and gate-on voltage or data signal pulse width and a frequency of a reference clock signal are corrected according to the temperature of the panel. The corrected quantity of gate-on voltage according to the polarity of write data or the corrected quantity of data signal pulse width is determined according to the temperature of the panel. The higher the temperature of the panel is, to the lower value the positive or negative gate-one voltage is set and the lower the temperature of the panel is, to the higher value the positive or negative gate-on voltage is set. Positive gate-on voltage is set so that it is always higher than negative gate-on voltage.

1. A method of driving a liquid crystal display panel comprising plural pixel electrodes connected to plural thin-film transistors for switching that are switched according to a pulse width modulation driving system, wherein:
 a positive gate-on voltage (V GONP ) and a negative gate-on voltage (V GONN ) of the thin-film transistors are set based upon the temperature of the liquid crystal display panel, wherein the positive gate-on voltage (V GONP ) is set so that it is higher than the negative gate-on voltage (V GONN ); and 
 as the temperature of the liquid crystal display panel rises, both the positive gate-on voltage (V GONP ) and the negative gate-on voltage (V GONN ) are set so that they are lower than before the rise of the panel temperature, while maintaining the relationship therebetween. 
 
   
   
     2. A method of driving a liquid crystal display panel comprising plural pixel electrodes connected to plural thin-film transistors for switching that are switched according to a pulse width modulation driving system, wherein the method comprises:
 setting a positive gate-on voltage (V GONP ) and a negative gate-on voltage (V GONN ) of the thin-film transistors based upon the temperature of the liquid crystal display panel, wherein the positive gate-on voltage (V GONP ) and the negative gate-on voltage (V GONN ) of the thin-film transistors are set so that the ON-state current (I ON ) of the thin-film transistors is fixed independent of the temperature of the panel; and 
 using the pulse width modulation driving system for modulating the pulse width of a data signal. 
 
   
   
     3. The method of driving a liquid crystal display according to  claim 2 , wherein:
 a positive data pulse width (T WP ) of the data signal in all displayed gradations is set so that it is longer than a negative data pulse width (T WN ) of the data signal; and 
 as the temperature of the panel rises, the positive gate-on voltage (V GONP ) and the negative gate-on voltage (V GONN ) of the thin-film transistor are set so that they are lower. 
 
   
   
     4. The method of driving a liquid crystal display according to  claim 2 , wherein
 a positive data pulse width (T WP ) and a negative data pulse width (T WN ) of the data signal allocated to each displayed gradation are set according to the temperature of the liquid crystal display panel. 
 
   
   
     5. The method of driving a liquid crystal display according to  claim 2 , wherein:
 a positive data pulse width (T wp ) of the data signal in all displayed gradations is set so that it is longer than a negative data pulse width (T WN ) of the data signal; and 
 as the temperature of the liquid crystal display panel rises, both the positive data pulse width (T WP ) and the negative data pulse width (T WN ) are set to be shorter than their respective pulse widths before the rise of the panel temperature, while maintaining the relationship therebetween. 
 
   
   
     6. The method of driving a liquid crystal display according to  claim 2 , wherein
 a positive data pulse width (T WP ) of the data signal in all displayed gradations is set so that it is longer than a negative data pulse width (T WN ) of the data signal. 
 
   
   
     7. A method of driving a liquid crystal display comprising plural pixel electrodes connected to plural thin-film transistors for switching that are switched according to a pulse width modulation driving system and a thin-film transistor for monitoring formed at the same time as the thin-film transistors for switching and disposed on the liquid crystal display panel, wherein the method comprises:
 setting a positive gate-on voltage (V GONP ) and a negative gate-on voltage (V GONN ) of the thin-film transistors based upon the temperature of the liquid crystal display panel; 
 using the pulse width modulation driving system for modulating the pulse width of a data signal; and 
 using the thin-film transistor for monitoring for setting the positive gate-on voltage (V GONP ) and the negative gate-on voltage (V GONN ) of the thin-film transistors for switching so that the ON-state current (I ON ) of the thin-film transistors for switching. 
 
   
   
     8. The method of driving a liquid crystal display according to  claim 7 , wherein a positive data pulse width (T WP ) of the data signal in all displayed gradations is set so that it is longer than a negative data pulse width (T WN ) of the data signal. 
   
   
     9. The method of driving a liquid crystal display according to  claim 7 , wherein:
 a positive data pulse width (T WP ) of the data signal in all displayed gradations is set so that it is longer than a negative data pulse width (T WN ) of the data signal; and 
 as the temperature of the panel rises, the positive gate-on voltage (V GONP ) and the negative gate-on voltage (V GONN ) of the thin-film transistor are set so that they are lower. 
 
   
   
     10. The method of driving a liquid crystal display according to  claim 7 , wherein a positive data pulse width (T WP ) and a negative data pulse width (T WN ) of the data signal allocated to each displayed gradation are set according to the temperature of the liquid crystal display panel. 
   
   
     11. The method of driving a liquid crystal display according to  claim 7 , wherein:
 a positive data pulse width (T wp ) of the data signal in all displayed gradations is set so that it is longer than a negative data pulse width (T WN ) of the data signal; and 
 as the temperature of the liquid crystal display panel rises, both the positive data pulse width (T WP ) and the negative data pulse width (T WN ) are set to be shorter than their respective pulse widths before the rise of the panel temperature, while maintaining the relationship therebetween. 
 
   
   
     12. A method of driving a liquid crystal display panel comprising plural pixel electrodes connected to plural thin-film transistors for switching that are switched according to a pulse width modulation driving system, wherein the method comprises:
 setting a positive gate-on voltage (V GONP ) and a negative gate-on voltage (V GONN ) of the thin-film transistors based upon a temperature of the liquid crystal display panel; 
 using the pulse width modulation driving system for modulating the pulse width of a data signal, wherein:
 each displayed gradation is represented by the number of clocks; 
 a reference clock signal is counted by a counter; 
 gradation data and the output of the counter are compared and the pulse width (T W ) of the data signal is set; and 
 a frequency of the reference clock signal is varied according to the temperature of the liquid crystal display panel provided by a temperature detecting means. 
 
 
   
   
     13. The method of driving a liquid crystal display according to  claim 12 , wherein
 the positive gate-on voltage (V GONP ) is set so that it is higher than the negative gate-on voltage (V GONN ). 
 
   
   
     14. The method of driving a liquid crystal display according to  claim 12 , wherein
 a positive data pulse width (T WP ) of the data signal in all displayed gradations is set so that it is longer than a negative data pulse width (T WN ) of the data signal. 
 
   
   
     15. A method of driving a liquid crystal display panel comprising plural pixel electrodes connected to plural thin-film transistors for switching that are switched according to a pulse width modulation driving system, wherein the method comprises:
 setting a positive gate-on voltage (V GONP )and a negative gate-on voltage (V GONN ) of the thin-film transistors based upon a temperature of the liquid crystal display panel; 
 using the pulse width modulation driving system for modulating the pulse width of a data signal, wherein:
 each displayed gradation is represented by the number of clocks; 
 a reference clock signal is counted by a counter; 
 gradation data and the output of the counter are compared and the pulse width (T W ) of the data signal is set; and 
 a frequency of the reference clock signal is set using a thin-film transistor for monitoring formed at the same time as the thin-film transistors for switching so that the frequency is proportional to the ON-state current (I ON ) of the thin-film transistor for monitoring. 
 
 
   
   
     16. The method of driving a liquid crystal display according to  claim 15 , wherein
 the positive gate-on voltage (V GONP ) is set so that it is higher than the negative gate-on voltage (V GONN ). 
 
   
   
     17. The method of driving a liquid crystal display according to  claim 15 , wherein
 a positive data pulse width (T WP ) of the data signal in all displayed gradations is set so that it is longer than a the-negative data pulse width (T WN ) of the data signal. 
 
   
   
     18. A method of driving a liquid crystal display panel comprising plural pixel electrodes connected to plural thin-film transistors for switching that are switched according to a pulse width modulation driving system, wherein:
 a positive gate-on voltage (V GONP ) and a negative gate-on voltage (V GONN ) of the thin-film transistors are set based upon the temperature of the liquid crystal display panel; and 
 as the temperature of the liquid crystal display panel rises, the center (V COM  center) of common voltage supplied to a common electrode of the liquid crystal display panel is made higher.